We have a very complex form on our website which is being generated using Formidable Forms (Pro version). It has a lot of conditional logic being used, and is very heavy in scripting as well as validation on the front end. An additional complexity is that after we submit the form, it pushes almost everything into a WooCommerce Subscription.

The company wants me to re-do the form as a custom implementation, i.e. remove the usage of Formidable forms, and custom implement the complexity, add validation both client and server side, move many things over to AJAX, and then repopulate the form if validation fails. Additionally, save the data into a custom DB table, and then be able to pick it up and repopulate the form if needed. Because many things are JSON based, using the back button in the navigation should also work.

Is that even a good idea? We would be re-inventing the wheel!

What are some of the challenges and complexities I will face if we decide to go ahead with this? I am fairly new to PHP and initial research is proving to me this can get quite complicated? Is there anything I can, as a novice, miss?

I am also after the correct way of doing this. Google reserach tells me I should either make a template or create a plugin for this purpose.